Male reproductive potential in the Black Sea turbot (Scophthalmus maximus) spawning populations

The combined analysis of biological characteristics and sperm traits of wild turbot males during spawning periods from mid-April to mid-June 2008, 2010, 2012–2014 in the local populations at the depths 50–95 m in the Northern Black Sea was carried out on the basis of the gillnet catches. Only mature males were observed during all sampling months and years. Gonadosomatic index of mature males with total body length 36–64 cm (aged 3–13-years-old) varied within 0.2–2.6. Sperm volume stripped from spermiating males ranged from 0.3 to 7.5 ml; sperm density and relative stripped production of spermatozoa fall in the range of 0.2–11 × 109 ml−1 and 0.4–46 × 109 per male, correspondingly. Principal component analysis indicated that neither biological characteristics of males, nor the phase of the spawning season impact the percentage of motile spermatozoa and сurvilinear velocity VCL in activated sperm. However, the best sperm traits (significantly higher, p < 0.05, than that of the sperm traits of males in other years) with average percentage of motile spermatozoa 95% (73 – 99.8%), average VCL 140 µm.s−1 (92–222 µm.s−1) was determined for males in 2010.